light reflex vs reflex response

light reflex and reflex response both are nouns.

Word	Noun	Adjective	Verb	Adverb
light reflex	Yes	No	No	No
reflex response	Yes	No	No	No

As nouns, reflex response is a hypernym of light reflex; that is, reflex response is a word with a broader meaning than light reflex:

light reflex: reflex contraction of the sphincter muscle of the iris in response to a bright light (or certain drugs) causing the pupil to become smaller
reflex response: an automatic instinctive unlearned reaction to a stimulus

light reflex (noun)	reflex response (noun)
reflex contraction of the sphincter muscle of the iris in response to a bright light (or certain drugs) causing the pupil to become smaller	an automatic instinctive unlearned reaction to a stimulus